In order to conserve space, documents are often stored photographically with their size greatly reduced on microfilm, microfiche, or other media. Such processes and media are known generally by the term micrographics.
In order to utilize a document which has been stored in micrographic format, a projector or reader is required. Such a reader will produce an enlarged reproduction of the reduced image on a screen for viewing by the operator. Often such readers also include a printer. When a desired document has been located by projection onto the screen the operator may produce a permanent enlarged copy through photographic or plain paper copier techniques. Systems which permit such reading and printing are known as reader/printers. The term reader/printer will be used herein to denote both readers containing only a projector and those including a printer in addition to a projector.
A problem which arises in the use of such systems relates to the fact that different reduction factors may be used in recording the micrographic images. As a result different magnifications are required in order to properly reproduce such images. In order to accommodate such variations, lenses having a variety of magnifications are commonly provided with micrographic reader/printers. In some cases as many as fifteen or more lenses are required to accommodate all possible reduction factors which may be used. The frequent changing of lenses can create a great inconvenience to operators of such equipment and can increase the time required for reading and printing documents stored in micrographic form.